One Hour Electric Bike Conversion; Installing a Kit

Editor Note: This is a repost of an important story we did back in our early days which shows a Mac geared motor kit being installed in one hour.

If you have been considering installing a hub motor on your bike, but hesitate because of the time and complexity involved in converting it…check out “The One Hour Electric Bike Conversion Procedure“. This Electric Bike conversion procedure is designed to be simple and quick. The entire process is performed in about an hour. Follow the steps below to see a good quality dual suspension mountain bike become a high powered off road electric bike.

The finished electric bike is capable of 30 miles per hour unassisted speed on level ground, traveling about 25 miles per charge. The project consists of installation of a geared brushless hub motor, lithium battery, motor control electronics and battery mounting system. The entire process from standard bike to fully functional e-bike takes about one hour. The bike shown was converted on the back deck of a rental cabin and went on a grueling off road ride in Armstrong Woods state park immediately after conversion.

The following tools are recommended for Electric Bicycle building and repair

First remove the rear wheel. This step simply consists of removing the bicycle wheel to be replaced with the hub motor equipped wheel. Most hub motors are sold as built wheels so lacing the wheel is not necessary.

The hub motor has an unusual axle shape with two flat spots that slide into the rear drop out. It will be more difficult to install than a standard wheel because the flat spots must be lined up with the bicycle drop out unlike a standard round bicycle axle. It may be necessary to widen the drop out with a flat file to allow the motor axle to drop down completely.

The force of the motor acts on the bicycle frame. It is common to spread or break the drop outs during heavy acceleration. The best way to prevent damaging the drop out is to add a torque arm. In this case the hub motor was run at stock power level of 1000 watts and the bicycle drop outs were exceedingly thick so a torque arm was not installed. We always recommend using a torque arm.

Make sure to tighten the axle nut with extra force. Use a large wrench to get extra leverage. Of course too much force will strip the axle nut. A long wrench will provide enough mechanical advantage to properly tighten the axle nut with minimal exertion. If you are unsure how much to tighten the nut, use a torque wrench and tighten to 50 ft-lbs.

The hub motor wires exit on the non drive side of the wheel on almost all hub motors. You will find 3 thick wires and 5 thinner wires on a sensored motor, and only 3 thick wires on a sensorless motor. The plugs and wire colors may not match if you use a controller and motor from different manufacturers. If you buy a complete kit, everything will be plug and play. The parts shown are a BMC sensored motor and BMC controller sold as a complete kit. All wire colors and plugs match as would be expected from a complete kit. Again the thick wires are called phase wires, the fine wires are called hall sensor wires. Sensorless motors only have the three thick phase wires.

Install a rack which will serve to hold the battery pack and controller. To accomplish a one hour conversion, a seat post clamp type rack is necessary. A standard bolt on rack will hold additional weight, but…requires custom fabrication work to be fitted to a dual suspension frame. Tighten the clamp firmly. The rack will have a tendency to swing forward when you ride on bumpy roads if the clamp is not tight enough.

The rack and padded bag used on this build were sold as a set, and fit together nicely. The padded bag will serve to hold both the battery pack and controller with some room to spare.

Place the battery in the bag. The battery shown is a fully managed 48-volt / 10-amp hour Lithium Iron Phosphate Battery (LiFePO4). See our up-coming battery article for help in choosing the most suitable battery for your build. This 10 lb battery will propel the bicycle for about 20 miles with little or no pedaling. Recharge time is about 2 hours from empty. There is no battery maintenance or battery memory effects.

Insert foam blocks around the battery to keep it from bouncing around too much when the bike is ridden off road. Use foam from electronics packaging or foam floor mat material and cut it to size.

Now the controller will be mounted to the bike bag. The controller needs good air flow so it cannot be placed inside the sealed compartment of the bike rack bag. The controller is waterproof so it can be mounted almost anywhere on the bike. I chose the netted pouch on the top of the bag because it hides the controller and wires while allowing good airflow.

Cut a slit in the bottom of the netted pocket to allow the wires to pass through to the main compartment of the bag. Make another slit at the bottom of the main compartment of the bag and pass the wires under the rack . Wire routing will be different if you a use different bag / rack as shown .

Familiarize yourself with the plugs. It is good to know which plug does what in case you run into problems.

Make the connections either below the seat or inside the rack bag. Zip-tie the wiring to the rack before and after the plugs. A loose plug is easily snagged and disconnected, which would cause the system to lose power immediately.

Remove the right side handlebar grip. Cut the rubber handlebar grip shorter to accommodate the throttle grip (if you have the “half grip” style shown). Install the throttle grip. Tighten the set screw with an allen wrench to prohibit the grip from moving around during heavy riding. Run the throttle wire with the brake and shifter cable to the rear of the bike. Use zip-ties to keep the wires tight to the bicycle. Always try to keep wires away from possible snags and abrasions routing along with brake and shifter cables is a safe bet.

The battery power plug is connected and disconnected to turn the system on and off if no switch is provided on the controller. It would seem logical to install an on/off switch between the battery and controller, but…the arcing that is caused when power is switched tends to make standard on/off switches fail after only a few uses. Expect to see a blue arc and hear a sharp pop noise when you connect the battery and controller to turn on the bike (the higher the voltage of the battery, the bigger the spark when connecting). This is normal.

The Finished eBike is an impressive and highly capable vehicle that can take you places that no dirt bike or 4WD truck is permitted to drive.

Eric has been involved in the electric bike industry since 2002 when he started a 6000 square foot brick and mortar Electric Bike store in downtown San Francisco. He is a true believer that small electric vehicles can change the way we operate and the way we think.

13 Comments

( September 26, 2012 )

I missed the part where the torque arm was actually installed. I did not see it in the final shot. I did not see the flat file in the tool list. If the drop out needed to be filed, wouldn’t this make the install time much longer? Where was the soldering iron used? Is that all of the tools, parts and supplies necessary to do a good job soldering? The connector is being pitted every time the battery is connected to the controller this way. How do you turn the system on and off without ruining the connector? If this job was going to be done properly with a reasonable amount of time for the additional tasks, wouldn’t 4 to 6 hours be a more reasonable estimate of how long this would take?

( December 12, 2013 )

( December 14, 2013 )

Alison Arellano

( March 30, 2015 )

I have 1000w 48v electric motor bike no battery i use it 1 time but my battery wont last long because my battery is only 6 AH, the bike is KHS alite1000 and I am selling it. if you have a lithium Ion 48v 1000w battery this is ready to go! price is $600 and pick up only..